The present invention relates to an apparatus for measuring reactions and/or diffusion experienced by particles suspended in a fluid for the purpose of measuring cells.
Known cell measuring apparatus includes a tapered pipe through which flows the suspension and a first entraining fluid for hydrodynamically focusing the suspension into a thin stream of suspension in which the particles are arranged in a single file and which, after leaving the pipe, is brought to an outlet together with the first entraining fluid. Such apparatus further includes an illumination and/or observation beam which intersects the thin stream of suspension, and at least one detector connected to a pulse evaluation circuit for detecting the radiation emanating from the individual particles.
Apparatus of this type is disclosed in my German Offenlegungsschrift [Laid-open Application] No. 2,543,310 and counterpart U.S. Pat. No. 4,110,043. However, this device is capable only, inter alia, of counting and classifying individual particles. It cannot be used to measure the movement of substances into and out of the particles, which may be cells, or chemical reactions at the particles because, on the one hand, the reaction fluid causes the illuminating and/or observation beam to be absorbed and, on the other hand, a minimum diameter would have to be maintained for the first entraining fluid to assure stabilization of the hydrodynamic focus. Therefore in this prior art apparatus this entraining fluid cannot be used as the reaction fluid.
In the past, such measurements were successful only when performed on individual particles with direct microscopic observation, as described by Elli Kohen et al in the section "Quantitative Aspects of Rapid Microfluorometry for the Study of Enzyme Reactions and Transport Mechanisms in Single Living Cells," of the text Fluorescence Techniques in Cell Biology, published by Springer Verlag, 1973, Heidelberg-New York, 5, at pages 207-17. This method employed dye reactions, radioactive or immunological techniques.
Such techniques or measurements can be employed only with individual particles which are not necessarily representative of the total quantity of particles or, if measurements are made with particles in suspension, do not permit any detailed information to be obtained about the individual particles.